1. Field of the Invention
The present invention relates to a tone synthesizing system which prevents their dynamic range from becoming excessively wide with an increase in the number of tablet select switches being simultaneously selected in a digital electronic musical instrument of the type synthesizing a waveshape through a discrete Fourier transfer.
2. Description of the Prior Art
To obtain a desired musical waveshape, there has heretofore been used an electronic musical instrument of the type that the amplitude values at sample points of the waveshape are computed through utilization of a waveshape synthesizing system employing a discrete Fourier transfer as disclosed, for instance, in U.S. Pat. No. 4,085,644. In the tone tablet selection of such an electronic musical instrument, a linear addition of tones calls for a wide dynamic range and an increase in the number of bits used introduces complexity in the circuit structure and naturally raises the manufacturing costs. And another problem is a feeling of incongruity which is produced when the volume rapidly increases with an increase in the number of tones as a result of such a linear addition. In contrast thereto, in order to prevent that musical signals are added as they are, there have been proposed a method in which tone tablet switches are used as a plurality of contacts and one of them is employed to vary the entire signal level as in a conventional analog organ, for instance, and a method of directly controlling an output signal in accordance with the number of tone tablet switches used as disclosed, for example, in Japanese Patent Application No. 37519/1976 (Pat. Laid-Open No. 120,818/1977). These methods control an analog output signal, and hence they possess defects in accuracy and mixture of noise.